JP4413883B2 - Sampling frequency converter - Google Patents

Description

  The present invention relates to a sampling frequency converter for converting data sampled at a certain sampling frequency into data of another sampling frequency suitable for a power protection relay device, for example.

  In a multi-frequency data sampling method as a conventional sampling frequency converter, for example, 10 kHz sampling frequency data is 600 blocks for commercial frequency 50 Hz, and 500 data is 1 block for 60 Hz, A method has been proposed in which sampling is performed with good separation by sampling data of three periods of each frequency (see, for example, Patent Document 1).

JP-A-5-19003 (paragraph numbers 0007, 0008, FIG. 2 and FIG. 3)

  In the conventional data sampling method as described above, data corresponding to both frequencies of 50/60 Hz is obtained by obtaining n samples in the m cycles of the alternating current. This method is effective when past data is processed to evaluate abnormal failure points, as in the case of evaluation, but when processing is performed using real-time sampling data that changes from time to time, the follow-up of conversion is high. Bad and not appropriate. In addition, since the calculation of the relay device uses data corresponding to an electrical angle obtained by dividing 90 ° by an integer of 1 or more, such as 30 ° or 45 °, an integer kHz (for example, 1 kHz, Sampling frequency of 2kHz, 10kHz, etc. is not divisible by 30 ° (720Hz for 60Hz system), 45 ° (480Hz for 60Hz system), 90 ° (240Hz for 60Hz system). In order to obtain data having a sampling frequency suitable for the operation of the relay device because data cannot be obtained, it is necessary to develop a new operation algorithm.

Furthermore, when a system is adopted in which digital signals of electrical quantities such as CT and PT of the substation are taken into the substation LAN (local area network) and input to the relay device, the CT and PT signals are the oscilloscope and relay. The same sampling data is applied to the device, etc., and the same sampling data is applied. In that case, the sampling of the electrical input is not suitable for the relay device, and is unified with the output standard of other devices (for example, oscilloscope devices) In this case, the relay device needs to convert a digital signal having a sampling frequency that is not a sampling frequency for the relay device that has been conventionally applied to a sampling frequency suitable for the operation of the relay device.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a sampling frequency conversion device that can easily convert data sampled at a certain sampling frequency into data at another sampling frequency. To do.

  In the sampling frequency converter according to the present invention, data for extracting digital data obtained by sampling an alternating current or voltage at a predetermined sampling frequency and converting the analog data at the sampling point into analog to digital as extraction data according to a predetermined rule Extraction means, data storage means for storing extraction data, data selection means for selecting three of the extraction data, sampling point time of one extraction data of the selected three extraction data, and selected 3 Calculation means for calculating the amplitude value, frequency and phase angle of current or voltage from two extracted data, and calculation of current or voltage at a calculation point after a predetermined time from a predetermined base point based on the predetermined time, amplitude value, frequency and phase angle A calculation data generating means for generating data is provided.

  Also, data extraction means for sampling alternating current or voltage at a predetermined sampling frequency, and extracting analog data at the sampling point from analog to digital as extracted data according to a predetermined rule, data for storing extracted data Storage means, data selection means for selecting two of the extracted data, time of sampling point of one of the two selected extracted data, and amplitude of current or voltage from the two selected extracted data Calculation means for calculating value, frequency and phase angle, and calculation data generation means for generating current or voltage at a calculation point after a predetermined time from a predetermined base point as calculation data based on the predetermined time, amplitude value, frequency and phase angle It is provided.

  According to the present invention, data extraction means for sampling AC current or voltage at a predetermined sampling frequency and extracting analog data from the analog data at the sampling point as analog-to-digital data as extraction data in accordance with a predetermined rule is stored. Data storage means for selecting, data selection means for selecting three of the extracted data, sampling point time of one extracted data of the three selected extracted data, and current or voltage from the three selected extracted data Calculation means for calculating the amplitude value, frequency, and phase angle, and calculation data generation for generating current or voltage at a calculation point after a predetermined time from a predetermined base point as calculation data based on the predetermined time, amplitude value, frequency, and phase angle Sampled at a certain sampling frequency. Data can be easily converted into data of another sampling frequency.

  Also, data extraction means for sampling alternating current or voltage at a predetermined sampling frequency, and extracting analog data at the sampling point from analog to digital as extracted data according to a predetermined rule, data for storing extracted data Storage means, data selection means for selecting two of the extracted data, time of sampling point of one of the two selected extracted data, and amplitude of current or voltage from the two selected extracted data Calculation means for calculating value, frequency and phase angle, and calculation data generation means for generating current or voltage at a calculation point after a predetermined time from a predetermined base point as calculation data based on the predetermined time, amplitude value, frequency and phase angle Data sampled at a certain sampling frequency. It is possible to simplify the operation process is possible easily converted to data of another sampling frequency, to shorten the calculation time.

Embodiment 1 FIG.
1 to 3 show a first embodiment for carrying out the present invention. FIG. 1 is a configuration diagram showing a configuration of a relay device including a sampling frequency converter, and FIG. 2 is a diagram of the sampling frequency converter. FIG. 3 is an explanatory diagram for explaining the operation of the sampling frequency converter. In FIG. 1, the current and voltage of the power line 1 are detected by CT2 and PT3, and the current and voltage signals are converted into digital data by converting analog data sampled at a predetermined sampling frequency by the AD conversion unit 4 into a communication network 5. To each device. In the relay device 9, the sampling frequency conversion device 10 (detailed configuration will be described later) converts the data into another sampling frequency data suitable for the relay device, and then uses the converted current and voltage digital data to calculate the operation circuit of the relay device. The calculation for the protection operation is executed at 7 and output to the relay by the output circuit 8, and the power line 1 is opened and closed by controlling a circuit breaker (not shown).

  As shown in FIG. 2, the sampling frequency conversion apparatus 10 includes a preprocessing unit 11, a preprocessing data storage unit 12, a calculation three-point selection unit 13, and a relay device calculation data generation unit 14. Next, the operation will be described. The preprocessing means 11 converts the input sampling data A having a sampling frequency p (Hz) into extracted data D having a sampling frequency f (Hz) suitable for the operation of the relay device. That is, the preprocessing means 11 obtains the extracted data D having a frequency P / n (= F) (Hz) that satisfies P / n> G> G / (n + 1).

  This means that, for example, when n = 2, every other input sampling data A is obtained, that is, extracted. When n = 3, the input sampling data A is extracted once every three times. In the case of n = m, it can be realized by extracting once in m times. The preprocessing data storage unit 12 stores the input sampling data A extracted by the preprocessing unit 11 from the input sampling data A as extracted data D. The calculation three-point selection means 13 selects the extracted data D at the three extraction points immediately before the point to be calculated (hereinafter referred to as the calculation point) according to the elapsed time from the predetermined calculation base point, and selects the selected data. Output as C1. The relay device calculation data generation means 14 calculates calculation data E for calculation of the relay device based on the selection data C1. The calculation data E is an estimated value obtained by calculation and is output to the relay device calculation circuit 7 (FIG. 1).

  This calculation will be described with reference to FIG. 3, the input sampling data A is input from the AD converter 4 (FIG. 1) to the preprocessing means 11 at the sampling frequency p, and the preprocessing means 11 extracts the extracted data d1, d2, d3,. Extracted as Sampling points (hereinafter referred to as extraction points) from which the extracted data d1, d2, d3,... Are sampled are defined as f1, f2, f3,. It is assumed that calculation points for which calculation data is to be obtained are calculation points g1, g2, g3,... And calculation data to be calculated corresponding to the calculation points g1, g2, g3,. Further, it is assumed that the extraction base point f1 = g1 and the data d1 = g1 for extracting the extraction data from the input sampling data A.

Here, the calculation data g2 is obtained by calculation. First, the extraction data d0, d1, and d2 at the three extraction points f0, f1, and f2 immediately before the calculation point g2 are selected by the calculation three-point selection means 13.
The data of the extraction points f0, f1, and f2 is d0 = A · sin (ωt + θ−θf)
d1 = A · sin (ωt + θ)
d2 = A · sin (ωt + θ + θf)
θf = Δf · Q · 360 ° (Q is the system frequency of power line 1, usually 50 Hz or 60 Hz, Δf is the sampling interval of d1 (f1), d2 (f2), d3 (f3), ---)
Therefore, A, ω, θ can be obtained from d0, d1, d2 by the relay device calculation data generation means 14. Here, A is the amplitude value of the signal, ω is the angular frequency (= Q · 360 °), and θ is the phase angle at the base point f1.
From this, the relay device calculation data generation means 14
e2 = A · sin (ωt + θ + θg)
θg = Δg · Q · 360 (Δg is the sampling interval of e1 (g1), e2 (g2), e3 (g3), ---)
The calculation data e2 can be obtained based on the above.

  Similarly, the operation data e3 can be obtained from the data d1, d2, d3. In the example of FIG. 3, since the point immediately before the point g4 is f5, it is not obtained from the data d2, d3, d4 but is obtained from the data d3, d4, d5.

  FIG. 3 is an explanatory diagram showing the situation. In the example of FIG.

That is, if the calculation data em is calculated from the extraction data dn−2, dn−1, dn at the extraction points fn−2, fn−1, fn,
When n · Δg <m · Δg <(n + 1) · Δf, the calculation data em + 1 is obtained from the extraction data dn-1, dn, dn + 1 at the extraction points fn-1, fn, fn + 1.
In the case of (n + 1) · Δg <m · Δg <(n + 2) · Δf, from the extracted data dn, dn + 1, dn + 2 at the extraction points fn, fn + 1, fn + 2,
calculate.
In this way, the data of the three previous extraction points are selected by the calculation three-point selection means 13 in accordance with the elapsed time from the base point f1, and the frequency ω of the calculation data e for calculation of the relay device is selected from the three extraction points. , Find the amplitude A and the phase angle θ,
em + 1 = A · sin (ωt + θ + θg)
θg = m · Δg · Q · 360
The calculation data em + 1 can be obtained by calculating as follows.

  As described above, in the sampling frequency conversion apparatus of this embodiment, the input sampling data A (a1, a2, a3,...) Having an arbitrary sampling frequency is sampled by the preprocessing means 11 according to a predetermined rule and extracted data. D (d1, d2, d3,...) Is obtained. The calculation three-point selection means 13 selects extracted data of three consecutive extraction points immediately before the calculation point gm, which is a time point at which the calculation data should be obtained from the extracted data D (d1, d2, d3,...). And output as selection data C1. The relay device calculation data generation means 14 generates calculation data E having a sampling frequency suitable for the calculation of the relay device based on the selection data C1. In this way, the input sampling data A sampled at an arbitrary sampling frequency can be easily converted into the calculation data E having a sampling frequency suitable for the relay device. The relay device 9 can execute a calculation for protective relay based on calculation data E of a sampling frequency suitable for the relay device calculation circuit 7.

Embodiment 2. FIG.
4 and 5 show the second embodiment of the present invention. FIG. 4 is a block diagram showing the configuration of the sampling frequency converter, and FIG. 5 is an explanatory diagram for explaining the operation of the sampling frequency converter. It is. In FIG. 4, the sampling frequency conversion device 20 has a calculation three-point selection means 23. This sampling frequency converter 20 is used instead of the sampling frequency converter 10 in FIG. Since other configurations are the same as those of the first embodiment shown in FIG. 1, the same reference numerals are given to the corresponding components and the description thereof is omitted.

  In the first embodiment, the frequency, amplitude, and phase angle of the extracted data D are calculated from the extracted data dn, dn + 1, dn + 2 at the three extracted points immediately before the calculation point, for example, fn, fn + 1, fn + 2, and these frequencies, amplitude, phase The calculation data em at the calculation point gm is obtained by inputting the time value of the calculation point gm into the calculation formula expressed as a function of the angle. In this embodiment, the extraction immediately before the calculation point gm is performed. Instead of the point fn + 2, a calculation point gm to be obtained is set between the middle extraction point fn + 1 and the third extraction point fn + 2 among the three extraction points, and the calculation data em is obtained. In this way, the followability of the sampling data can be improved even when a sudden change in data occurs, so that a more accurate estimated value can be obtained.

  FIG. 5 is an explanatory view showing the situation. In the example of FIG.

That is, if the data em at the calculation point eg is calculated from the extraction data dn-1, dn, dn + 1 at the extraction points fn-1, fn, fn + 1, the calculation data em + 1 at the calculation point gm + 1 is
In the case of n · Δg <m · Δg <(n + 1) · Δf, from the extracted data dn, dn + 1, dn + 2 of the extraction points fn, fn + 1, fn + 2,
In the case of (n + 1) · Δg <m · Δg <(n + 2) · Δf, from the extracted data dn + 1, dn + 2, dn + 3 of the extraction points fn + 1, fn + 2, fn + 3,
calculate.
In this way, the extraction data of the three extraction points before and after the calculation point obtained by the elapsed time from the base point is selected by the calculation three-point selection unit 13, and the above three extraction points are selected by the relay device calculation data generation unit 14. Obtain the frequency ω, amplitude A, and phase angle θ from the extracted data.
em + 1 = A.sin (ωt + θ + θg)
θg = m · Δg · Q · 360
The calculation data em + 1 can be obtained by calculating.

Embodiment 3 FIG.
6 and 7 show a third embodiment of the present invention, FIG. 6 is a block diagram showing the configuration of the sampling frequency converter, and FIG. 7 is an explanatory diagram for explaining the operation of the sampling frequency converter. It is. In FIG. 6, the sampling frequency conversion device 30 includes a calculation two-point selection unit 33 and a relay device calculation data generation unit 34. This sampling frequency converter 30 is used instead of the sampling frequency converter 10 in FIG. The calculation two-point selection means 33 selects the extracted data of the two previous extraction points. The relay device calculation data generation means 34 obtains the amplitude value and phase angle of the extraction data D from the extraction data of the two extraction points selected by the calculation two-point selection means 33. Since other configurations are the same as those of the first embodiment shown in FIG. 1, the same reference numerals are given to the corresponding components and the description thereof is omitted.

  In the first and second embodiments, the frequency, amplitude, and phase angle of the extracted data D are calculated from the extracted data at three extraction points immediately before the calculation point, and the calculation data is expressed as a function of these frequency, amplitude, and phase angle Although the calculation data em at the calculation point gm is obtained by inputting the time value gm to be calculated into the calculation formula of em, in Embodiment 3, since the frequency of the power system of the commercial frequency is known, The amplitude and phase angle of the extraction data D are calculated from the extraction data of the two extraction points immediately before the point, and the calculation formula of the calculation data em expressed as a function of the frequency, amplitude, and phase angle of the known power system is obtained. The calculation value em of the calculation point gm is obtained by inputting the time of the calculation point gm.

The operation will be described with reference to FIG. First, an extraction base point for extracting data from the input sampling data A is f1, and f1 = g1.
Extracted data d1 and d2 of the two extraction points f1 and f2 selected by the calculation two-point selection means 33 are:
d1 = A · sin (ωt + θ)
d2 = A · sin (ωt + θ + θf)
θf = Δf · Q · 360 ° (Q is the power line frequency of 50 Hz or 60 Hz)
Therefore, A and θ can be obtained from the extracted data d1 and d2. Here, A is the amplitude value of the signal, ω is the frequency, and θ is the phase angle at the base point f1.
E2 = A · sin (ωt + θ + θg)
θg = Δg · Q · 360
To obtain e2.

  FIG. 7 is an explanatory diagram showing the situation. In the example of FIG.

That is, if the calculation data em is calculated from the extraction data dn-1, dn at the extraction points fn-1, fn,
The calculation data em + 1 is
In the case of n · Δg <m · Δg <(n + 1) · Δf, from the extracted data dn and dn + 1 at the extraction points fn and fn + 1,
In the case of (n + 1) · Δg <m · Δg <(n + 2) · Δf, the extracted data dn + 1 and dn + 2 at the extraction points fn + 1 and fn + 2
From
calculate.
Thus, the relay device calculation data generation means 34 obtains the sampling amplitude A and the phase angle θ of the calculation data e from the extraction data of the two extraction points according to the elapsed time from the base point f1,
em + 1 = A · sin (ωt + θ + θg)
θg = m · Δg · Q · 360
The calculation data em + 1 can be obtained by calculating.
By making the number of data used for the calculation two, it is possible to simplify the calculation process and shorten the calculation time.

Embodiment 4 FIG.
8 and 9 show a fourth embodiment of the present invention. FIG. 8 is a block diagram showing the configuration of the sampling frequency converter, and FIG. 9 is an explanatory diagram for explaining the operation of the sampling frequency converter. It is. In FIG. 8, the sampling frequency conversion device 40 has a calculation two-point selection means 43. The calculation two-point selection means 43 selects data of two extraction points before and after the calculation point. In the third embodiment, the data to be obtained is estimated from the data of the two extraction points immediately before the time to be obtained. In this embodiment, however, the calculation data is obtained from the extraction data of the two extraction points before and after the calculation point as shown in FIG. This is what is required and has the same effect.

  FIG. 9 is an explanatory diagram showing the situation. In the example of FIG.

That is, if the calculation data em is calculated from the extraction data dn and dn + 1 at the extraction points fn and fn + 1,
The calculation data em + 1 is
In the case of n · Δg <m · Δg <(n + 1) · Δf, from the extracted data dn + 1 and dn + 2 at the extraction points fn + 1 and fn + 2,
In the case of (n + 1) · Δg <m · Δg <(n + 2) · Δf, from the extracted data dn + 2 and dn + 3 at the extraction points fn + 2 and fn + 3,
calculate.
In this way, the amplitude A and the phase angle θ of the extraction data D are obtained from the extraction data of the two extraction points according to the elapsed time from the base point,
em + 1 = A.sin (ωt + θ + θg)
θg = m · Δg · Q · 360
Em + 1 can be obtained by calculating.
In this way, by calculating the calculation data of the calculation point from the data of the two extraction points before and after the calculation point, the followability to the sampling data that changes transiently is improved.

Embodiment 5 FIG.
10 and 11 show the fourth embodiment of the present invention. FIG. 10 is a block diagram showing the configuration of the sampling frequency converter, and FIG. 11 is an explanatory diagram for explaining the operation of the sampling frequency converter. It is. In FIG. 10, the sampling frequency converter 50 includes relay calculation data generation means 54. The relay calculation data generation means 54 calculates calculation data E based on the extracted data C selected by the calculation two-point selection means. In the third embodiment, the time from the calculation base point is used to calculate the calculation data. However, in this embodiment, the time difference between the extraction point of the extraction data with the earlier time and the calculation point among the selected extraction data. Is used.

  FIG. 11 is an explanatory diagram showing the situation. In the example of FIG.

That is, the calculation data em is calculated from the extraction data dn and dn + 1 at the extraction points fn and fn + 1. If the time difference between fn + 2 and em at that time is Xm−1, the calculation data em + 1 is obtained by the relay calculation data generation means 54 (1 ) When Xm−1 + Δf> Δg, the amplitude A and the phase angle θ of the operation data em + 1 are obtained from the extracted data dn + 1 and dn + 2 at the extraction points fn + 1 and fn + 2.
em + 1 = A.sin (ωt + θ + θg)
θg = (2Δg−Δf−Xm−1) · Q · 360
To obtain operation data em + 1.
(2) When Xm−1 + Δf <Δg The amplitude A and the phase angle θ of the operation data em + 1 are obtained from the extracted data dn + 2 and dn + 3 at the extraction points fn + 2 and fn + 3,
em + 1 = A.sin (ωt + θ + θg)
θg = (2Δg−Xm−1) · Q · 360
To obtain operation data em + 1.
(3) When xm + Δf = Δg Since gm + 1 = fn + 2, em + 1 = dn + 2.

As described above, the extraction data of the two extraction points immediately before the calculation point are selected, the amplitude A and the phase angle θ of the extraction data D are obtained, and the calculation data em + 1 is calculated from the time difference between the earlier extraction point and the calculation point gm + 1. The calculation data em + 1 can be obtained by calculating the phase angle θg and substituting the phase angle θg into the calculation formula of the calculation data em + 1. In the above, the time difference between the earlier extraction point of the two extraction points and the calculation point gm is used, but the later extraction point (that is, the one closer to the calculation data) of the two extraction points is used as a time reference. The calculation point data may be obtained from the time difference from the calculation point gm + 1. In this case, the time difference between the later one and the calculation point is calculated by subtracting Δf from the time difference between the earlier one and the operation point. In this way, by using the phase angle difference obtained from the time difference between the extraction point and the calculation point of the extraction data used for calculating the calculation data, the accumulated error from the extraction base point and the calculation base point is not dragged, and more accurate. High computation is possible.
In the first embodiment, the calculation data can be calculated using the time difference between any one of the three extraction points and the calculation point. Even in this case, the accumulated error from the extraction base point and the calculation base point is not dragged, and more accurate calculation is possible.

Embodiment 6 FIG.
FIGS. 12 and 13 show the sixth embodiment of the present invention, FIG. 12 is a block diagram showing the configuration of the sampling frequency converter, and FIG. 11 is an explanatory diagram for explaining the operation of the sampling frequency converter. It is. In FIG. 13, the sampling frequency converter 60 includes relay calculation data generation means 64. The relay calculation data generation means 64 calculates calculation data E based on the extracted data C selected by the calculation two-point selection means. In the fifth embodiment, the calculation data is calculated by using two points immediately before the calculation base point, but two points before and after the calculation base point are used.

  FIG. 13 is an explanatory diagram showing the situation. In the example of FIG.

That is, the calculation data em is calculated from the extraction data dn and dn + 1 of the extraction points fn and fn + 1. If the time difference between fn + 1 and em at that time is xm, the calculation data em + 1 is obtained by the relay calculation data generation means 64 (1) Xm When -1 + Δf> Δg, the amplitude A and the phase angle θ of the operation data em + 1 are obtained from the extraction data dn + 1 and dn + 2 at the extraction points fn + 1 and fn + 2.
em + 1 = A.sin (ωt + θ + θg)
θg = (Δf−Xm) · Q · 360
However, Xm = Xm−1 + Δf−Δg
To obtain operation data em + 1.
(2) When Xm−1 + Δf <Δg, the amplitude A and the phase angle θ of the calculation data em + 1 are obtained from the extraction data dn + 2 and dn + 3 at the extraction points fn + 2 and fn + 3,
em + 1 = A.sin (ωt + θ + θg)
θg = (Δf−Xm) · Q · 360
However, Xm = Xm−1 + 2Δf−Δg
To obtain operation data em + 1.
(3) When Xm−1 + Δf = Δg Since gm + 1 = fn + 2, em + 1 = dn + 2.

As described above, the extraction data of the two extraction points before and after the calculation point are selected, the amplitude A and the phase angle θ of the extraction data D are obtained, and the phase of the calculation data em + 1 is calculated from the time difference between the previous extraction point and the calculation point gm + 1. The calculation data em + 1 can be obtained by calculating the angle θg and substituting the phase angle θg into the calculation formula of the calculation data em + 1. In this way, by using the phase angle difference obtained from the time difference between the extraction point and the calculation point of the extraction data used for calculating the calculation data, the accumulated error from the extraction base point and the calculation base point is not dragged, and more accurate. High computation is possible.
In the second embodiment, the calculation data can be calculated using the time difference between any one of the three extraction points and the calculation point. Even in this case, the accumulated error from the extraction base point and the calculation base point is not dragged, and more accurate calculation is possible.
Further, in each of the above embodiments, the extraction data at the extraction point immediately before and after the calculation point is used. However, the extraction data immediately before and immediately after must be used, and the object of the present invention is impaired. It is also possible to use extraction data at an extraction point further before the previous time and extraction data at an extraction point further after the previous time within a range that does not exist.

It is a block diagram of the relay apparatus containing the sampling frequency converter which is Embodiment 1 of this invention. It is a block diagram of the sampling frequency converter of FIG. It is explanatory drawing for demonstrating operation | movement of the sampling frequency converter of FIG. It is a block diagram of the sampling frequency converter which is Embodiment 2 of this invention. It is explanatory drawing for demonstrating operation | movement of the sampling frequency converter of FIG. It is a block diagram of the sampling frequency converter which is Embodiment 3 of this invention. It is explanatory drawing for demonstrating operation | movement of the sampling frequency converter of FIG. It is a block diagram of the sampling frequency converter which is Embodiment 4 of this invention. It is explanatory drawing for demonstrating operation | movement of the sampling frequency converter of FIG. It is a block diagram of the sampling frequency converter which is Embodiment 5 of this invention. It is explanatory drawing for demonstrating operation | movement of the sampling frequency converter of FIG. It is a block diagram of the sampling frequency converter which is Embodiment 6 of this invention. It is explanatory drawing for demonstrating operation | movement of the sampling frequency converter of FIG.

Explanation of symbols

1 power line, 2 CT, 3 PT, 4 AD converter, 7 relay arithmetic circuit,
8 output circuit, 9 relay device,
10, 20, 30, 40, 50, 60 Sampling ring frequency converter,
11 frequency conversion preprocessing means, 12 preprocessing data storage means,
13, 23 Three-point selection means for calculation,
14, 34, 54, 64 Relay calculation data generation means,
33, 43 Two-point selection means for calculation.

Claims (7)

Data extraction means for sampling an alternating current or voltage at a predetermined sampling frequency, and extracting digital data obtained by analog-to-digital conversion of analog data at the sampling point as extracted data according to a predetermined rule; data storage for storing the extracted data Means, data selection means for selecting three of the extracted data, time of the sampling point of one extracted data of the three selected extracted data, and the current from the three selected extracted data Or the calculation means for calculating the amplitude value, frequency and phase angle of the voltage, and the current or voltage at the calculation point after a predetermined time from a predetermined base point to the amplitude value, the frequency and the phase angle for the predetermined time. Sampling frequency with calculation data generating means for generating calculation data based on Conversion circuit. 2. The sampling frequency conversion circuit according to claim 1, wherein the data selection means selects extracted data at three sampling points before the predetermined time. 2. The sampling frequency conversion circuit according to claim 1, wherein the data selection means selects extracted data at two sampling points before and after the predetermined time. Data extraction means for sampling an alternating current or voltage at a predetermined sampling frequency, and extracting digital data obtained by analog-to-digital conversion of analog data at the sampling point as extracted data according to a predetermined rule; data storage for storing the extracted data Means, data selecting means for selecting two of the extracted data, time of the sampling point of one extracted data of the two selected extracted data, and the current from the two selected extracted data Or the calculation means for calculating the amplitude value, frequency and phase angle of the voltage, and the current or voltage at the calculation point after a predetermined time from a predetermined base point to the amplitude value, the frequency and the phase angle for the predetermined time. Sampling frequency with calculation data generating means for generating calculation data based on Conversion circuit. 5. The sampling frequency conversion circuit according to claim 4, wherein the data selection means selects extracted data at two sampling points before the predetermined time. 5. The sampling frequency conversion circuit according to claim 4, wherein the data selection means selects extracted data of one sampling point before and after the predetermined time. The calculation means obtains a time difference between the two sampling points or one of the three sampling points and the calculation point and calculates the current or the current from the time difference and the data of the two sampling points or the three sampling points. 7. The sampling frequency conversion circuit according to claim 1, wherein the voltage amplitude value and the phase angle are calculated.

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